In recent decades, automotive air conditioners have been developed rapidly and rank second in the air conditioning machinery. A heat exchanger, as one of the four main components of the automotive air conditioner, is also required to be improved to optimize the design according to the market requirements. The parallel flow heat exchanger has characteristics, such as a high cooling efficiency, a small size, a light weight and etc., thus can meet the requirements of the market quite well, and in recent years, it has been increasingly applied in the automotive air conditioning systems.
A conventional micro-channel heat exchanger mainly includes micro-channel flat tubes, fins and manifolds. Two ends of the micro-channel flat tubes are provided with a respective manifold for distributing and collecting the refrigerant. The corrugated or louver-shaped fins are provided between adjacent micro-channel flat tubes for improving the heat exchange efficiency between the condenser and the air.
A bent heat exchanger is disclosed in U.S. Pat. No. 5,531,268 announced on Jul. 2, 1996, which includes an inlet manifold, an outlet manifold, fins and flat tubes. The flat tubes at the same layer are each formed integrally by bending, and each includes a first portion connected to the inlet manifold, a second portion connected to the outlet manifold, and a bent portion which is twisted and located at the middle. The first portion and the second portion of the flat tube are both connected to the fins, and the bent portion thereof is a finless section. In the bent heat exchanger, the inner side and the outer side of the bent portion both have an arc shape. However, in this design, the bending process of the flat tube has a low precision, which is apt to cause a partial deformation of the heat exchanger, damage structures of the fins nearby, and thus the heat exchange efficiency is reduced. Furthermore, the flat tube bent by the above manner may have a large protruding dimension after the arc-shaped bent portions are overlapped with each other, and the external dimension of the heat exchanger cannot be accurately controlled, which ultimately results in installation difficulties. Most importantly, the above manner forming the arc bending portion requires a large bending length to be reserved, and it is well known that a portion of the flat tube connected to the fins has a better heat exchange performance compared to the finless section, thus for a flat tube having a fixed length, if a length of a fined section is increased, a length of a finless section is decreased accordingly, which reduces the heat exchange performance of the heat exchanger.
With the continuous development of technology, customers have imposed increasingly high requirements on the heat exchange performance of the heat exchanger, and the structure of the heat exchanger disclosed in the above patent is difficult to adapt to the current requirements. Therefore, it is necessary to optimize the structure of the conventional bent heat exchanger and the method for bending the heat exchanger.